An inductor motor using a permanent magnet in a rotor has been known. In such an inductor motor 9, for example, as shown in FIGS. 14 and 15, a stator block 91 including stators 911 and 912 holding an excitation coil 910 therebetween, and a stator block 92 including stators 921 and 922 holding an excitation coil 920 therebetween are stacked in two rows, and a substantially columnar rotor 93 having an outer peripheral surface multi-pole magnetized so that N-poles and S-poles are circumferentially alternately arranged is placed inside the stator blocks 91 and 92 (for example, see Patent Document 1).
As shown in FIGS. 14 and 15, the stators 911, 912, 921 and 922 each have a plurality of stator teeth protruding in the stacking direction on substantially the same circumference. FIG. 15 shows an imaginary arrangement of the stator teeth unrolled on a plane. In the stator blocks 91 and 92, the stator 911 (921) and the stator 912 (922) are placed to face each other so that their stator teeth protruding toward each other interdigitate with each other. In the inductor motor 9, as shown in FIG. 15, a phase of the stator block 92, that is, a position in a rotational direction thereof is shifted from that of the stator block 91. A phase difference G between the stator block 91 and the stator block 92 is set, for example, to a rotation angle corresponding to one forth of a formation pitch of the stator teeth.
In the inductor motor 9 configured as described above, energizing the excitation coil 910 (920) magnetizes the facing stator 911 (921) and stator 912 (922) to have different polarities. Specifically, in the stator block 91 (92), the stator teeth arranged on the same circumference can be circumferentially alternately magnetized to N-poles or S-poles.
In the inductor motor 9, the excitation coils 910 and 920 are energized according to a predetermined sequence to alternately switch polarities of the stator teeth with time. Alternately switching the polarities of the stator teeth allows repeated attraction or repulsion between the N-poles or the S-poles on the outer peripheral surface of the rotor 93 and the stator teeth. Then, the running torque of the rotor 93 can be generated on the basis of an attractive force or a repulsive force applied to the N-poles and the S-poles on the outer peripheral surface of the rotor 93. In the inductor motor 9, as described above, the stator blocks 91 and 92 are stacked in the shifted manner in the rotational direction, and thus the rotor 93 can be rotated in a predetermined direction.
The stators 911, 912, 921 and 922 that are components of the inductor motor 9 are each formed of, for example, a substantially flat plate-shaped member of a magnetic material by boring a hole in the member to leave a plurality of protruding pieces protruding inwardly, and then bending the protruding pieces from their roots to stand up. By such machining steps using the substantially flat plate-shaped member, inexpensive stators can be extremely efficiently produced by press working such as stamping or bending. The inductor motor 9 using the inexpensive stators 911, 912, 921 and 922 can be a product with high cost performance.
However, the conventional inductor motor has the following problem. Specifically, in the inductor motor using the stator formed of the substantially flat plate-shaped member, a length of the stator teeth is limited by an outer diameter of the inductor motor, and therefore the running torque that can be outputted may not be sufficiently ensured depending on the outer diameter.
Patent Document 1: Japanese Patent Laid-open No. 10-84663